1. Field of the Invention
The invention relates to a heater.
2. Background Art
EP 0 313 764 A2 teaches a heater, which comprises a component fitted with permanent magnets and joined to a rotor shaft which is mounted for rotation in a casing. Individual soft iron cores are disposed in the casing. A heat transfer medium, in particular cooling water, flows around the soft iron cores inside the casing. Practice has shown that this arrangement helps translate mechanical energy into heat only to a very limited extent.
An eddy-current brake is known from the lexicon "Maschinenbau, VDI Verlag 1995, ISBN 3-401372-3, page 1430", which is an electric brake of non-contact operation, translating mechanical energy into heat by eddy currents in a metallic mass. By design the eddy-current brake is an internal-pole-type d.c. generator. In this case, a stationary inner ring supports a coil through which passes direct current and which produces a homopolar magnetic field. An armature ring of electrically conductive material constitutes the active part of a rotor. Upon rotation of the rotor relative to a stator, eddy currents are induced in the armature ring, cooperating with the stator field to produce a braking moment, the range of which depends on the exciting current and the slip speed. Eddy-current brakes of this type are employed among others in trucks as an additional brake on the propeller shaft.
A heater is known from PCT application WO99/10971 (no prior publication), having a casing with an interior chamber, a cooling-water supply connector and a cooling-water discharge connector opening into the interior chamber. A rotatably drivable rotor shaft is mounted for rotation in the casing. Two component parts are provided, which are coaxial to the axis and one part of which is provided with permanent magnets, while the other part is a closed ring of electrically conductive material disposed at least partially in the interior chamber. One of these parts is non-rotatably disposed as a rotor on the rotor shaft. The parts are rotary relative to each other, leaving a gap between the permanent magnets and the part of electrically conductive material.
DE 196 00 735 A teaches a cooling-water pump for an internal combustion engine, which comprises a bearing casing for the shaft of an impeller. A belt pulley is mounted on the outer end of the shaft. A heater, which is embodied as a so-called Visco-heater, is disposed as a substantially independent additional set on the bearing casing.